javascript - 单击选择选项时如何显示/隐藏 div

Question

我有一个选择框，当您单击一个选项时，我想在隐藏的 div 中显示帮助文本:

<select  onchange="optionCheck()" multiple="multiple" name="test" id="options" size="15" class="form-select">
    <option value="1">option 1</option>
    <option value="2">option 2</option>
</select>

<div id="help1" style=visibility:hidden>help text 1</div>
<div id="help2" style=visibility:hidden>help text 2</div>

<script type="text/javascript">
    function optionCheck(){
        var option = document.getElementById("options").value;
        if(option == "1"){
            document.getElementById("help1").style.visibility ="visible";
            document.getElementById("help2").style.visibility ="hidden";
        }
        if(option == "2"){
            document.getElementById("help2").style.visibility ="visible";
            document.getElementById("help1").style.visibility ="hidden";
        }
    }
</script>

如何创建一个简单的循环，这样我就不必为每个选项编写“if”语句？

 document.getElementById(option).style.visibility ="visible";

不工作 - javascript 和我相处得不好 ;-)

此外，是否有一种简单的方法可以在选择一个选项时隐藏所有其他 div？

Answer 1

我建议使用一些 CSS 类来隐藏/显示 div。然后 JavaScript 只需要为每个 div 设置 class 属性。

如果您选择多个选项，此解决方案仍然有效。

HTML:

<select onchange="optionCheck()" multiple="multiple" name="test" id="options" size="15" class="form-select">
    <option value="1">option 1</option>
    <option value="2">option 2</option>
</select>

<div id="help1" class="helpText">help text 1</div>
<div id="help2" class="helpText">help text 2</div>

CSS:

/* consider "display: none/block" instead of visibility: hidden/visible
   if you don't want the hidden divs to occupy space */
.helpText {
    visibility: hidden;
}
.helpTextShow {
    visibility: visible;
}​

JavaScript:

function optionCheck() {
    var i, len, optionVal, helpDiv,
        selectOptions = document.getElementById("options");

    // loop through the options in case there
    // are multiple selected values
    for (i = 0, len = selectOptions.options.length; i < len; i++) {

        // get the selected option value
        optionVal = selectOptions.options[i].value;

        // find the corresponding help div
        helpDiv = document.getElementById("help" + optionVal);

        // move on if we didn't find one
        if (!helpDiv) { continue; }

        // set CSS classes to show/hide help div
        if (selectOptions.options[i].selected) {
            helpDiv.className = "helpText helpTextShow";
        } else {
            helpDiv.className = "helpText";
        }
    }    
}

// alternative method of binding the onchange handler, merely a suggestion
//document.getElementById("options").onchange = optionCheck;

这是一个用于演示的 jsFiddle:http://jsfiddle.net/willslab/3N9pm/9/

希望对您有所帮助!